Television system and apparatus



Dec. 24, 1935. H, R N E 2,025,027

TELEVISION SYSTEM AND APPARATUS Filed March 6, 1933 2 SheetsSheet l r vV U.

INVENTOR f araldfiflanla,

E L N O D P H TELEVISION SYSTEM AND APPARATUS Filed March 6, 1931) 2Sheets-Sheet 2 INVENTOR fiaraldflfiamj Patented Dec. 24, 1935 UNITEDSTATES ATENT OFFIQE Harold P. Donle, Meriden, Conn, assignor to RadioInventions, Inc., a corporation of New York Application March 6, 1930,Serial No. 433,670

6 Claims.

The invention relates to improvements in television and comprises amethod and apparatus for producing an image of greater detail than theusual scanning methods allow and therefore of better quality.

An object of this invention is the production of greater image detailwithout requiring radical or costly changes in the dimensions or speedof a given television apparatus.

Another object of this invention is to produce virtual optical aperturesof slit-like form in moving elements such as discs or drums as used inscanning, without the expensive and elaborate mechanical processesinvolved in the accurate production and alignment of such apertures, asfor example by punching or cutting as heretofore practiced.

Another object of my invention is to allow the actual physical slitsemployed in scanning members to be of such width as to be readily formedby ordinary mechanical modes of working the materials used in thesescanning members, and yet have the optical slit resultant from the useof my invention of much narrower width than the physical slits, andallow this width to beadjusted at will.

Another object of my invention is to produce the average view in betterapparent detail than possible with equi-dimensional elements of scanningand the same maximum frequency transmission requirements.

Another object of my invention as used at a transmitter is to secure amore nearly correct analysis so that better reproduction will take placeeven with ordinary equi-dimensional scanning elements at the receiver.

Other objects and advantages of this invention will appear from thefollowing specification:

In the accompanying drawings Fig. 1 is a plan view of one form oftransmitting device for scanning motion picture film, embodying thisinvention.

Fig. 2 illustrates diagrammatically the elementary picture areasproduced by a scanning device such as the ordinary Nipkow disc, withround scanning apertures.

Fig. 3 shows the elementary areas produced by a scanner with squareapertures and ordinary low detail.

Fig. 4 is a diagrammatic representation of the approximate elementaryareas produced by one form of my invention, illustrating the high detailin the horizontal dimension, as compared with Figs. 2 and 3.

Fig. 5 is an elevation detail of the scanning aperture arrangement ofFig. 1, showing coacting apertures.

Fig. 6 shows in perspective a single optical slot as produced by thisinvention.

Fig. '7 shows in perspective a scanning aperture 5 defined in twodimensions, as produced by one form of this apparatus, the parts beingdisassembled to more clearly illustrate their mutual relationship.

Fig. 8 shows the shape of the optical aperture produced by the device ofFig. 7.

It is a Well known and fundamental principle of television scanning thatthe smaller the size of the individual element, the better detail theresultant reproduced image will have. Certain l5 structural, optical,and electrical difficulties have limited the practically feasibleminimum size of an element, and it has hitherto been the practice tokeep the detail the same in both dimensions, i. e., to use either roundor square apertures.

I have discovered that an increase of detail in one dimension only isattended by an apparent improvement in detail throughout the image,

. and that the psychological phenomena involved cause the apperceptionof an image of improved quality without analyzing its dimensionallimitations. In fact, by an apparent psychological compensatory transferof values, some highly exceptional image, such as the figure with radiallines of uniform width used in ordinary optometric measurements, isnecessary in order for the mental apperception of the received image toevoke any reaction in the observer of dimensional inequality of degreeof detail. Since such geometrical figures, or their equivalents, rarelyenter into images to be customarily transmitted, the validity of theinvention remains unimpugned in regard to its application to thetelevision transmission of ordinary object matter.

By the use of my invention I have made it a simple matter to increasethe number of elemental areas in one dimension of the picture withoutradical change of apparatus designed for low detail scanning,

I have devised means to readily and economi- 'cally secure a virtualscanning aperture of the small width necessary to accomplish the purposeof high detail, without having recourse to the expensive and difficultmechanical production of such an actual aperture with the desired degree59 of accuracy of dimensions and placement.

I have devised methods of combining the narrow virtual apertures of myinvention with devices giving lower detail scanning, so that acombination of both degrees of detail is readily available, thus takingadvantage of the psychological effects above mentioned.

I have found that for most characters of images to be transmitted thebest result is to be obtained by making the detail greatest in thehorizontal dimension, but do not limit the invention to high detail ineither dimension, or in one dimension only;

I accordingly provide a slitted'scanning member in which the slit is sonarrow that one dimension of the elementary scanning area is of smallermagnitude than the other dimension.

One method of providing such a narrow slit consists in the use of twoslitted members with the slits superposed but with one offset to adegree so that the virtual slit may be as narrow as described.

In Fig. 1 the driving motor I has its shaft 2 connected by a coupling 3to shaft 4, which rotates in bearings 9 and I2. A composite scanningdisc made up of two members or sections In and II combined ashereinafter indicated, is coupled at I3 to shaft 4. This shaft bears aworm 5 engaging with a gear 6 upon a shaft I4. Upon shaft I4 is a chainsprocket connected by a chain 8 with another chain sprocket I5. Thissprocket bears also on its shaft I6, film sprocket I1 and its motion istransmitted through spring belt l8 to film reel I9. The film 20 unreelsfrom reel 2| which releases it under slight tension'and passes overguide 22 and through edge guides 32, continuously passing by astationary slot 23 in a screen 33 supported on a bracket 34, ispropelled by film sprocket I! and is rewound upon reel I9. A lamp 25with'a luminous source 24, has its divergent rays 26 passing through acondenser system 21, whence they emerge as convergent rays 28 and areinterrupted in a predetermined fashion by scanning disc III, II so as toscan in one dimension the image on the film which is beingsimultaneously scanned, usually at a slow rate,

The luminous result of this a housing 3|.

Virtual slits 40 (Fig. 5) in the compmite disc pass by the stationaryslit 23. The film moves horizontally through guides 32, by thestationary slit 23.

In Fig. 6 a fragmentary view of the edge of the composite scanning discshows it made up of disc I0 and disc II which bears respectively thewide slits 4| and 42, so positioned relative to one another that theiroverlap or common optical opening 40 constitutes the virtual narrow slitof this invention. 'The actual slits 4| and 42 are readily made, due totheir width, and readily positioned with respect to the other slits onthe same disc. The two discs I0 and II may be identical except that Ilmay be mounted upon the collar I3 of Fig. 1 by a series of screws I3 inholes II, accuratelydetermining its placement, and the second disc I0may have mounting slots I0 instead of holes, allowing its angularadvancement or retardation in respect tothe first disc. This angulardisplacement is usually determined upon before operation of theapparatus and the discs then firmly fastened by screws I3 in the desiredangular relationship, in respect to one another and the common shaftrotating them.

Fig. '7 illustrates a mode of securing a composite scanning disc whichshall scan an image in both dimensions. It is apparent that such adevice is applicable to Fig. 1 only if the stationary slit 23 of thisfigure is omitted and the film operated so that each separate picturethereof remains stationary for the length of time required for suchscanning.

This form of my invention is especially suited for the scanning ofordinary three dimensional scenes, not previously optically enregisteredinto a series of two dimensional views, such as motion picture film, andalso to reproduce for purposes of visual viewing or projection, theimages transmitted by such a device as Fig. 1, or other type oftelevision transmitter. In this fragmentary disrupted view of the edgeof the composite scanning disc, discs I0 and II, with slits 4| and 42,are the same as formerly described, and have be- 16 tween them the disc50, which is of the ordinary Nipkow type. Holes 43 and 44 represent thefirst and last members of a spirally disposed series of holes in disc50. 7

These three discs may obviously be assemble in any order, as long as thetwo slits cooperate to form a virtual narrow slit and the holes in disc50 cooperate with this virtual slit, so thatv the slit bisects thecircular aperture.

It is evident from Figs. 7 and 8 that-such narrow virtual apertures willappear in a spiral formation as the composite disc revolves, thus scanning an image in two dimensions without auxiliary scanning apertures inany member other than the composite disc. .30"

image from a similar transmitter or from any transmitter giving properspacing between successive scannings, by appropriate change of partssuch as the substitution of a light reproducing source as customarilyused in television receivers, v for the light source 24 shown in thisfigure, the to elimination of the light-sensitive cell and propershielding of the film from light other than that passing thru thescanning apertures.

It is possible to use mechanical devices for changing theangularrelationship of the two discs making up the composite scanningdisc, while these discs are in motion, similar to the device shown in mycopending application 425,785 filed Feb. 4, 1930. This device will allowthe width of the virtual optical slit to be changed while in operation,according to the available or desired relationship between the degree ofdetail and other factors entering into consideration, such as degree ofillumination, frequency width of channels of communication and othervariables.

A similar phase shifting device can be applied to the composite disc ofFigs. 7 and 8, with corresponding results. 7

Synchronization between transmitter and receiver can be obtained in anyof the usual ways, or by the method described in my copendingapplication 322,360 filed Nov. 28, 1928.

Framing of the received image may be accomplished by many methods.Rotation of the field of the driving motor, or change of angularrelationship of the entire rotating disc, as a whole with respect to thedriving shaft, by mechanical means as mentioned supra are two possiblemethods. It is also possible to produce a r-eduplicated image with thedisc of Fig. 7, by making the spiral of holes of more than oneconvolution, and to select the single image desired, by a movableaperture, substantially in accordance with the principles set forth inmy above mentioned copending application #a25,785.

Other modes of construction of the rotating member can be used. Forexample a composite rotating hollow drum, made up of two drums with setsof Wide slits overlapping to produce a set of narrow virtual opticalslits can be used in conjunction with a fixed stationary slit for motionpicture film transmission. A composite drum consisting of two slitteddrums .as just described and a third drum with helically disposedcircular apertures can be used as the sole scanning member.

Apertures of square cross section can be substituted for the round holesin any of the foregoing devices. This invention can be readily appliedto scanning systems using two moving members, such as the one outlinedin my copending application #425,785.

To secure more perfect parallelism of the sides of the virtual slit, theactual physical slits producing this aforesaid virtual slit may havetheir sides tapered to an appropriate degree and in an appropriatedirection to oifset the error due to the radial character of theirlateral boundary lines, which error results in a trapezoidal figure,instead of .a true parallelogram. This error is usually so slight,however, that its correction is unnecessary.

To facilitate clear illustration, the thickness of the component discshas been shown in the drawings as greater relative to the otherdimensions, than it would be in practice. Actually the discs would be asthin as consistent with mechanical strength and rigidity.

While not confining this improvement to any definite ratios ofelementary unit size in the two dimensions, yet its advantages becomemost marked when this ratio exceeds two to one, and a ratio as high asten to one has been employed. The upper limit of this ratio is partiallydetermined by the maintenance of a satisfactory relationship between thelight transmitted through an elementary optical unit, and the photoelectric cell response. This in turn is related to the intensity of thelight source and the sensitivity of the light cell. Likewise,considerations of the frequency transmission characteristics of thecommunication channel or channels employed, the electricalcharacteristics of the amplifying systems and other terminal apparatus,all enter into the choice of a suitable ratio, and in general set anupper feasible limit for this ratio in any given case.

Wherever the foregoing explanations and descriptions of my invention areillustrated by actual sizes and details of apparatus as employed inexperimental use, such details are not to be considered as in any Waylimiting the scope of my invention, which consists broadly in theemployment of elementary scanning areas of a different mensuration intwo dimensions, and in the method of securing the relatively smalleroptical apertures needed for the lesser of said two dimensions by theproper superposition of physical apertures having a size great enough topermit of their economical and easy production.

I claim:

1. A television scanning device including a moving scanning member, saidmember having a spirally disposed series of optical openings therein,

said openings being defined in one dimension by two parts fixed withrelation to one another having slits, the slits in one part cooperatingwith the slits in the other part to define an optical aperture, andbeing defined in the other dimension by a part fixed with relation tothe other two previously mentioned parts having a spirally disposedseries of openings cooperating with said optical apertures resultantfrom said parts having slits, in order to produce said series ofspirally disposed optical openings suited to scan an image by therotation of the scanning member.

2. Television scanning apparatus, including a member having a slit fordetermining the vertical dimension of an elemental scanning area, saidslit being in motion relative to the image to be scanned, and a memberhaving a series of slits of substantially uniform width not more thanhalf the optical width in their smallest dimension of the width of thesmallest dimension of the first mentioned slit, for determining thehorizontal dimension of said elemental scanning area, said series ofslits being in motion relative to the image to be scanned, in adirection substantially at right angles to the direction of motion ofthe first mentioned slit.

3. Television transmitting apparatus for use with motion picture filmcarrying successive images tobe transmitted, including means for movingsaid film at a substantially constant speed, a first member having afixed slit positioned substantially at right angles to the direction ofmotion of said film and acting to delimit one dimension of an elementaryscanning area, a second member having a slit positioned substantiallyparallel to the direction of motion of said film and acting to delimitthe other dimension of an elementary scanning area, means for movingsaid second slitted member at a rate proportional to the velocity ofsaid moving film and so that the slit therein optically intersects saidfixed slit, said moving slit having its smallest dimension not more thanone half the Width of the smallest dimension of said fixed slit, theratio of the widths of said two slits remaining substantially constantthroughout the transmission process.

4. A television scanner including means for moving a motion picture filmat a uniform rate of speed so as to produce a series of moving I imagesto be scanned, an optical screen having therein a slit past which saidimages move and acting to limit one dimension of an elementary scanningarea in the direction of motion of said images, a second optical screenhaving therein a slit acting to limit the other dimension of anelementary scanning area, said second slit limiting the other dimensionof said scanning area to a value not more than one half its firstmentioned dimension, and means for moving the slit in said second screentransversely of the slit in said first screen and at a rate of speedproportional to the speed of said film.

5. A television scanning system including two discrete scanning members,means for producing relative motion between both of said members and animage to be scanned so as to scan said image in two substantiallyperpendicular dimensions at two different rates of speed, optical meanslimiting the width of an elementary scanning area in the direction ofmore rapid scanning to a width not more than one half the width of saidarea in the direction of slower scanning, one of said scanning membersgiving substantially complete scanning in one dimension and the otherscanning member giving subment of said film, so as to scan said film insaid transverse direction, means for scanning said film in the otherdirection and optical means for delimiting an elementary scanning areato a substantially rectangular form, one of whose dlmen- 5 sions is atleast twice as great as the other.

HAROLD P. DONLE.

